The present invention relates to a duping arrangement or decoy device for laser distance measuring devices, and, more particularly, to a duping arrangement in which an identical but time-delayed signal is sent to the transmitter by the illuminated object.
Several types of duping arrangements are already known. They are based, however, on passive as well as active duping methods. The disadvantage of a passive construction utilizing mirrors is that the reflection energy is too low because of the small cross-sectional surface size of the entry optical system in proportion to the entire surface of the illuminated object. Known active constructions using lasers require relatively high expenditures because, for each possible wavelength of the arriving irradiation, a separate laser must be used that has the same wavelength.
DE-OS 24 08 058 shows a known interference method in which a laser distance measuring device is provided on the ground for combatting low-flying planes, and is combined with fire guiding radar. The interval between the first and the second ground laser pulse is determined and triggers an interference pulse in the case of a board laser which, when the third pulse of the ground laser is received, in a time-delayed manner, is beamed into the direction of the ground laser. This construction requires very high optical and electronic expenditures since the laser transmitter as well as the laser warning receiver, which is assigned specifically to this laser transmitter, must be equipped with their own optical system. In addition, amplifiers, frequency meters, a delay logic and special controls, and the like are also required.
DE-OS 36 09 834 shows another known construction in which the irradiation received as the laser measuring irradiation and to be affected by the interference is radiated as interference irradiation in a time delayed manner. For this purpose, a laser transmitter situated at the illuminated object is triggered by the delayed received irradiation, the delay being achieved by a fiber-optical wave guide of the desired length, or irrespective of the reception of a laser irradiation to be disturbed, uncorrelated laser interference pulses are emitted continuously into all directions of space. In this case also, the optical and electronic expenditures are considerable, apart from the fact that there exist the initially mentioned disadvantages for the previously known passive and active solutions.
It is an object of the present invention to provide a duping device which not only significantly reduces the optical and electronic expenditures but is also significantly improved with respect to its output and intensity.
The foregoing object is achieved by utilizing a duping arrangement comprising a wide-angle optical system, a fiber delay line and a phase-conjugated element.